1. Maturity does not mean that invention ceased, as the significant upturn in patenting in 1881 and 1882 indicates. Still, this upturn may have been a response to the expiration of another institution formed early in the product cycle, the patent pool.
2. When classified by kind of use, inventors varied little in the frequency of repeat patenting; virtually all the difference of repeat patenting rates is accounted for by variation among multiple inventors in the number of repeats. This contrasts with unused patents, for which the far lower frequency of repeat inventing accounts for somewhat over half of the lower rate. Perhaps use of any kind fostered repeat inventing, but the incentive and finance provided by larger-scale usage was decisive in the greater persistence of inventors for larger firms.
3. Table 5 differs from earlier tables because it focuses on inventors rather than patents; a patent issued to several individuals is counted separately for each patentee here but was counted only once in earlier tables. It also includes the 26 patents issued prior to 1853.
4. Companies with more outside agencies would of course be expected to learn more than those with fewer. To weigh the number of companies by the number of their agencies outside the state (or category of states) in any period would accentuate the importance of nodal states. The geographic concentration of production, a consequence of the growth of interstate agency systems, may also reflect the significance of interstate learning. Nodal states had by far the largest per capita employment in sewing machine manufacturing. From 1860 through 1880, they averaged 610 per million population, compared with 187 for secondary states and only 4 for tertiary states.
5. These conclusions also hold within categories of states. Southern tertiary states regularly had fewer first patents and agencies per capita than northern and western tertiary states. Likewise, among nodal states New York consistently had the fewest first patents and agencies per capita.